/*
** $Id: lstrlib.c,v 1.254.1.1 2017/04/19 17:29:57 roberto Exp $
** Standard library for string operations and pattern-matching
** See Copyright Notice in lua.h
*/

#define lstrlib_c
#define LUA_LIB

#include "lprefix.h"

#include <ctype.h>
#include <float.h>
#include <limits.h>
#include <locale.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "lua.h"

#include "lauxlib.h"
#include "lualib.h"

/*
** maximum number of captures that a pattern can do during
** pattern-matching. This limit is arbitrary, but must fit in
** an unsigned char.
*/
#if !defined(LUA_MAXCAPTURES)
#define LUA_MAXCAPTURES 32
#endif

/* macro to 'unsign' a character */
#define uchar(c) ((unsigned char)(c))

/*
** Some sizes are better limited to fit in 'int', but must also fit in
** 'size_t'. (We assume that 'lua_Integer' cannot be smaller than 'int'.)
*/
#define MAX_SIZET ((size_t)(~(size_t)0))

#define MAXSIZE (sizeof(size_t) < sizeof(int) ? MAX_SIZET : (size_t)(INT_MAX))

static int str_len(lua_State* L)
{
    size_t l;
    luaL_checklstring(L, 1, &l);
    lua_pushinteger(L, (lua_Integer)l);
    return 1;
}

/* translate a relative string position: negative means back from end */
static lua_Integer posrelat(lua_Integer pos, size_t len)
{
    if (pos >= 0)
        return pos;
    else if (0u - (size_t)pos > len)
        return 0;
    else
        return (lua_Integer)len + pos + 1;
}

static int str_sub(lua_State* L)
{
    size_t l;
    const char* s = luaL_checklstring(L, 1, &l);
    lua_Integer start = posrelat(luaL_checkinteger(L, 2), l);
    lua_Integer end = posrelat(luaL_optinteger(L, 3, -1), l);
    if (start < 1)
        start = 1;
    if (end > (lua_Integer)l)
        end = l;
    if (start <= end)
        lua_pushlstring(L, s + start - 1, (size_t)(end - start) + 1);
    else
        lua_pushliteral(L, "");
    return 1;
}

static int str_reverse(lua_State* L)
{
    size_t l, i;
    luaL_Buffer b;
    const char* s = luaL_checklstring(L, 1, &l);
    char* p = luaL_buffinitsize(L, &b, l);
    for (i = 0; i < l; i++) p[i] = s[l - i - 1];
    luaL_pushresultsize(&b, l);
    return 1;
}

static int str_lower(lua_State* L)
{
    size_t l;
    size_t i;
    luaL_Buffer b;
    const char* s = luaL_checklstring(L, 1, &l);
    char* p = luaL_buffinitsize(L, &b, l);
    for (i = 0; i < l; i++) p[i] = tolower(uchar(s[i]));
    luaL_pushresultsize(&b, l);
    return 1;
}

static int str_upper(lua_State* L)
{
    size_t l;
    size_t i;
    luaL_Buffer b;
    const char* s = luaL_checklstring(L, 1, &l);
    char* p = luaL_buffinitsize(L, &b, l);
    for (i = 0; i < l; i++) p[i] = toupper(uchar(s[i]));
    luaL_pushresultsize(&b, l);
    return 1;
}

static int str_rep(lua_State* L)
{
    size_t l, lsep;
    const char* s = luaL_checklstring(L, 1, &l);
    lua_Integer n = luaL_checkinteger(L, 2);
    const char* sep = luaL_optlstring(L, 3, "", &lsep);
    if (n <= 0)
        lua_pushliteral(L, "");
    else if (l + lsep < l || l + lsep > MAXSIZE / n) /* may overflow? */
        return luaL_error(L, "resulting string too large");
    else
    {
        size_t totallen = (size_t)n * l + (size_t)(n - 1) * lsep;
        luaL_Buffer b;
        char* p = luaL_buffinitsize(L, &b, totallen);
        while (n-- > 1)
        { /* first n-1 copies (followed by separator) */
            memcpy(p, s, l * sizeof(char));
            p += l;
            if (lsep > 0)
            { /* empty 'memcpy' is not that cheap */
                memcpy(p, sep, lsep * sizeof(char));
                p += lsep;
            }
        }
        memcpy(p, s, l * sizeof(char)); /* last copy (not followed by separator) */
        luaL_pushresultsize(&b, totallen);
    }
    return 1;
}

static int str_byte(lua_State* L)
{
    size_t l;
    const char* s = luaL_checklstring(L, 1, &l);
    lua_Integer posi = posrelat(luaL_optinteger(L, 2, 1), l);
    lua_Integer pose = posrelat(luaL_optinteger(L, 3, posi), l);
    int n, i;
    if (posi < 1)
        posi = 1;
    if (pose > (lua_Integer)l)
        pose = l;
    if (posi > pose)
        return 0;               /* empty interval; return no values */
    if (pose - posi >= INT_MAX) /* arithmetic overflow? */
        return luaL_error(L, "string slice too long");
    n = (int)(pose - posi) + 1;
    luaL_checkstack(L, n, "string slice too long");
    for (i = 0; i < n; i++) lua_pushinteger(L, uchar(s[posi + i - 1]));
    return n;
}

static int str_char(lua_State* L)
{
    int n = lua_gettop(L); /* number of arguments */
    int i;
    luaL_Buffer b;
    char* p = luaL_buffinitsize(L, &b, n);
    for (i = 1; i <= n; i++)
    {
        lua_Integer c = luaL_checkinteger(L, i);
        luaL_argcheck(L, uchar(c) == c, i, "value out of range");
        p[i - 1] = uchar(c);
    }
    luaL_pushresultsize(&b, n);
    return 1;
}

static int writer(lua_State* L, const void* b, size_t size, void* B)
{
    (void)L;
    luaL_addlstring((luaL_Buffer*)B, (const char*)b, size);
    return 0;
}

static int str_dump(lua_State* L)
{
    luaL_Buffer b;
    int strip = lua_toboolean(L, 2);
    luaL_checktype(L, 1, LUA_TFUNCTION);
    lua_settop(L, 1);
    luaL_buffinit(L, &b);
    if (lua_dump(L, writer, &b, strip) != 0)
        return luaL_error(L, "unable to dump given function");
    luaL_pushresult(&b);
    return 1;
}

/*
** {======================================================
** PATTERN MATCHING
** =======================================================
*/

#define CAP_UNFINISHED (-1)
#define CAP_POSITION (-2)

typedef struct MatchState
{
    const char* src_init; /* init of source string */
    const char* src_end;  /* end ('\0') of source string */
    const char* p_end;    /* end ('\0') of pattern */
    lua_State* L;
    int matchdepth;      /* control for recursive depth (to avoid C stack overflow) */
    unsigned char level; /* total number of captures (finished or unfinished) */
    struct
    {
        const char* init;
        ptrdiff_t len;
    } capture[LUA_MAXCAPTURES];
} MatchState;

/* recursive function */
static const char* match(MatchState* ms, const char* s, const char* p);

/* maximum recursion depth for 'match' */
#if !defined(MAXCCALLS)
#define MAXCCALLS 200
#endif

#define L_ESC '%'
#define SPECIALS "^$*+?.([%-"

static int check_capture(MatchState* ms, int l)
{
    l -= '1';
    if (l < 0 || l >= ms->level || ms->capture[l].len == CAP_UNFINISHED)
        return luaL_error(ms->L, "invalid capture index %%%d", l + 1);
    return l;
}

static int capture_to_close(MatchState* ms)
{
    int level = ms->level;
    for (level--; level >= 0; level--)
        if (ms->capture[level].len == CAP_UNFINISHED)
            return level;
    return luaL_error(ms->L, "invalid pattern capture");
}

static const char* classend(MatchState* ms, const char* p)
{
    switch (*p++)
    {
    case L_ESC:
    {
        if (p == ms->p_end)
            luaL_error(ms->L, "malformed pattern (ends with '%%')");
        return p + 1;
    }
    case '[':
    {
        if (*p == '^')
            p++;
        do
        { /* look for a ']' */
            if (p == ms->p_end)
                luaL_error(ms->L, "malformed pattern (missing ']')");
            if (*(p++) == L_ESC && p < ms->p_end)
                p++; /* skip escapes (e.g. '%]') */
        } while (*p != ']');
        return p + 1;
    }
    default:
    {
        return p;
    }
    }
}

static int match_class(int c, int cl)
{
    int res;
    switch (tolower(cl))
    {
    case 'a':
        res = isalpha(c);
        break;
    case 'c':
        res = iscntrl(c);
        break;
    case 'd':
        res = isdigit(c);
        break;
    case 'g':
        res = isgraph(c);
        break;
    case 'l':
        res = islower(c);
        break;
    case 'p':
        res = ispunct(c);
        break;
    case 's':
        res = isspace(c);
        break;
    case 'u':
        res = isupper(c);
        break;
    case 'w':
        res = isalnum(c);
        break;
    case 'x':
        res = isxdigit(c);
        break;
    case 'z':
        res = (c == 0);
        break; /* deprecated option */
    default:
        return (cl == c);
    }
    return (islower(cl) ? res : !res);
}

static int matchbracketclass(int c, const char* p, const char* ec)
{
    int sig = 1;
    if (*(p + 1) == '^')
    {
        sig = 0;
        p++; /* skip the '^' */
    }
    while (++p < ec)
    {
        if (*p == L_ESC)
        {
            p++;
            if (match_class(c, uchar(*p)))
                return sig;
        }
        else if ((*(p + 1) == '-') && (p + 2 < ec))
        {
            p += 2;
            if (uchar(*(p - 2)) <= c && c <= uchar(*p))
                return sig;
        }
        else if (uchar(*p) == c)
            return sig;
    }
    return !sig;
}

static int singlematch(MatchState* ms, const char* s, const char* p, const char* ep)
{
    if (s >= ms->src_end)
        return 0;
    else
    {
        int c = uchar(*s);
        switch (*p)
        {
        case '.':
            return 1; /* matches any char */
        case L_ESC:
            return match_class(c, uchar(*(p + 1)));
        case '[':
            return matchbracketclass(c, p, ep - 1);
        default:
            return (uchar(*p) == c);
        }
    }
}

static const char* matchbalance(MatchState* ms, const char* s, const char* p)
{
    if (p >= ms->p_end - 1)
        luaL_error(ms->L, "malformed pattern (missing arguments to '%%b')");
    if (*s != *p)
        return NULL;
    else
    {
        int b = *p;
        int e = *(p + 1);
        int cont = 1;
        while (++s < ms->src_end)
        {
            if (*s == e)
            {
                if (--cont == 0)
                    return s + 1;
            }
            else if (*s == b)
                cont++;
        }
    }
    return NULL; /* string ends out of balance */
}

static const char* max_expand(MatchState* ms, const char* s, const char* p, const char* ep)
{
    ptrdiff_t i = 0; /* counts maximum expand for item */
    while (singlematch(ms, s + i, p, ep)) i++;
    /* keeps trying to match with the maximum repetitions */
    while (i >= 0)
    {
        const char* res = match(ms, (s + i), ep + 1);
        if (res)
            return res;
        i--; /* else didn't match; reduce 1 repetition to try again */
    }
    return NULL;
}

static const char* min_expand(MatchState* ms, const char* s, const char* p, const char* ep)
{
    for (;;)
    {
        const char* res = match(ms, s, ep + 1);
        if (res != NULL)
            return res;
        else if (singlematch(ms, s, p, ep))
            s++; /* try with one more repetition */
        else
            return NULL;
    }
}

static const char* start_capture(MatchState* ms, const char* s, const char* p, int what)
{
    const char* res;
    int level = ms->level;
    if (level >= LUA_MAXCAPTURES)
        luaL_error(ms->L, "too many captures");
    ms->capture[level].init = s;
    ms->capture[level].len = what;
    ms->level = level + 1;
    if ((res = match(ms, s, p)) == NULL) /* match failed? */
        ms->level--;                     /* undo capture */
    return res;
}

static const char* end_capture(MatchState* ms, const char* s, const char* p)
{
    int l = capture_to_close(ms);
    const char* res;
    ms->capture[l].len = s - ms->capture[l].init; /* close capture */
    if ((res = match(ms, s, p)) == NULL)          /* match failed? */
        ms->capture[l].len = CAP_UNFINISHED;      /* undo capture */
    return res;
}

static const char* match_capture(MatchState* ms, const char* s, int l)
{
    size_t len;
    l = check_capture(ms, l);
    len = ms->capture[l].len;
    if ((size_t)(ms->src_end - s) >= len && memcmp(ms->capture[l].init, s, len) == 0)
        return s + len;
    else
        return NULL;
}

static const char* match(MatchState* ms, const char* s, const char* p)
{
    if (ms->matchdepth-- == 0)
        luaL_error(ms->L, "pattern too complex");
init: /* using goto's to optimize tail recursion */
    if (p != ms->p_end)
    { /* end of pattern? */
        switch (*p)
        {
        case '(':
        {                        /* start capture */
            if (*(p + 1) == ')') /* position capture? */
                s = start_capture(ms, s, p + 2, CAP_POSITION);
            else
                s = start_capture(ms, s, p + 1, CAP_UNFINISHED);
            break;
        }
        case ')':
        { /* end capture */
            s = end_capture(ms, s, p + 1);
            break;
        }
        case '$':
        {
            if ((p + 1) != ms->p_end)          /* is the '$' the last char in pattern? */
                goto dflt;                     /* no; go to default */
            s = (s == ms->src_end) ? s : NULL; /* check end of string */
            break;
        }
        case L_ESC:
        { /* escaped sequences not in the format class[*+?-]? */
            switch (*(p + 1))
            {
            case 'b':
            { /* balanced string? */
                s = matchbalance(ms, s, p + 2);
                if (s != NULL)
                {
                    p += 4;
                    goto init; /* return match(ms, s, p + 4); */
                }              /* else fail (s == NULL) */
                break;
            }
            case 'f':
            { /* frontier? */
                const char* ep;
                char previous;
                p += 2;
                if (*p != '[')
                    luaL_error(ms->L, "missing '[' after '%%f' in pattern");
                ep = classend(ms, p); /* points to what is next */
                previous = (s == ms->src_init) ? '\0' : *(s - 1);
                if (!matchbracketclass(uchar(previous), p, ep - 1) && matchbracketclass(uchar(*s), p, ep - 1))
                {
                    p = ep;
                    goto init; /* return match(ms, s, ep); */
                }
                s = NULL; /* match failed */
                break;
            }
            case '0':
            case '1':
            case '2':
            case '3':
            case '4':
            case '5':
            case '6':
            case '7':
            case '8':
            case '9':
            { /* capture results (%0-%9)? */
                s = match_capture(ms, s, uchar(*(p + 1)));
                if (s != NULL)
                {
                    p += 2;
                    goto init; /* return match(ms, s, p + 2) */
                }
                break;
            }
            default:
                goto dflt;
            }
            break;
        }
        default:
        dflt:
        {                                     /* pattern class plus optional suffix */
            const char* ep = classend(ms, p); /* points to optional suffix */
            /* does not match at least once? */
            if (!singlematch(ms, s, p, ep))
            {
                if (*ep == '*' || *ep == '?' || *ep == '-')
                { /* accept empty? */
                    p = ep + 1;
                    goto init; /* return match(ms, s, ep + 1); */
                }
                else          /* '+' or no suffix */
                    s = NULL; /* fail */
            }
            else
            { /* matched once */
                switch (*ep)
                { /* handle optional suffix */
                case '?':
                { /* optional */
                    const char* res;
                    if ((res = match(ms, s + 1, ep + 1)) != NULL)
                        s = res;
                    else
                    {
                        p = ep + 1;
                        goto init; /* else return match(ms, s, ep + 1); */
                    }
                    break;
                }
                case '+': /* 1 or more repetitions */
                    s++;  /* 1 match already done */
                          /* FALLTHROUGH */
                case '*': /* 0 or more repetitions */
                    s = max_expand(ms, s, p, ep);
                    break;
                case '-': /* 0 or more repetitions (minimum) */
                    s = min_expand(ms, s, p, ep);
                    break;
                default: /* no suffix */
                    s++;
                    p = ep;
                    goto init; /* return match(ms, s + 1, ep); */
                }
            }
            break;
        }
        }
    }
    ms->matchdepth++;
    return s;
}

static const char* lmemfind(const char* s1, size_t l1, const char* s2, size_t l2)
{
    if (l2 == 0)
        return s1; /* empty strings are everywhere */
    else if (l2 > l1)
        return NULL; /* avoids a negative 'l1' */
    else
    {
        const char* init; /* to search for a '*s2' inside 's1' */
        l2--;             /* 1st char will be checked by 'memchr' */
        l1 = l1 - l2;     /* 's2' cannot be found after that */
        while (l1 > 0 && (init = (const char*)memchr(s1, *s2, l1)) != NULL)
        {
            init++; /* 1st char is already checked */
            if (memcmp(init, s2 + 1, l2) == 0)
                return init - 1;
            else
            { /* correct 'l1' and 's1' to try again */
                l1 -= init - s1;
                s1 = init;
            }
        }
        return NULL; /* not found */
    }
}

static void push_onecapture(MatchState* ms, int i, const char* s, const char* e)
{
    if (i >= ms->level)
    {
        if (i == 0)                           /* ms->level == 0, too */
            lua_pushlstring(ms->L, s, e - s); /* add whole match */
        else
            luaL_error(ms->L, "invalid capture index %%%d", i + 1);
    }
    else
    {
        ptrdiff_t l = ms->capture[i].len;
        if (l == CAP_UNFINISHED)
            luaL_error(ms->L, "unfinished capture");
        if (l == CAP_POSITION)
            lua_pushinteger(ms->L, (ms->capture[i].init - ms->src_init) + 1);
        else
            lua_pushlstring(ms->L, ms->capture[i].init, l);
    }
}

static int push_captures(MatchState* ms, const char* s, const char* e)
{
    int i;
    int nlevels = (ms->level == 0 && s) ? 1 : ms->level;
    luaL_checkstack(ms->L, nlevels, "too many captures");
    for (i = 0; i < nlevels; i++) push_onecapture(ms, i, s, e);
    return nlevels; /* number of strings pushed */
}

/* check whether pattern has no special characters */
static int nospecials(const char* p, size_t l)
{
    size_t upto = 0;
    do
    {
        if (strpbrk(p + upto, SPECIALS))
            return 0;                 /* pattern has a special character */
        upto += strlen(p + upto) + 1; /* may have more after \0 */
    } while (upto <= l);
    return 1; /* no special chars found */
}

static void prepstate(MatchState* ms, lua_State* L, const char* s, size_t ls, const char* p, size_t lp)
{
    ms->L = L;
    ms->matchdepth = MAXCCALLS;
    ms->src_init = s;
    ms->src_end = s + ls;
    ms->p_end = p + lp;
}

static void reprepstate(MatchState* ms)
{
    ms->level = 0;
    lua_assert(ms->matchdepth == MAXCCALLS);
}

static int str_find_aux(lua_State* L, int find)
{
    size_t ls, lp;
    const char* s = luaL_checklstring(L, 1, &ls);
    const char* p = luaL_checklstring(L, 2, &lp);
    lua_Integer init = posrelat(luaL_optinteger(L, 3, 1), ls);
    if (init < 1)
        init = 1;
    else if (init > (lua_Integer)ls + 1)
    {                   /* start after string's end? */
        lua_pushnil(L); /* cannot find anything */
        return 1;
    }
    /* explicit request or no special characters? */
    if (find && (lua_toboolean(L, 4) || nospecials(p, lp)))
    {
        /* do a plain search */
        const char* s2 = lmemfind(s + init - 1, ls - (size_t)init + 1, p, lp);
        if (s2)
        {
            lua_pushinteger(L, (s2 - s) + 1);
            lua_pushinteger(L, (s2 - s) + lp);
            return 2;
        }
    }
    else
    {
        MatchState ms;
        const char* s1 = s + init - 1;
        int anchor = (*p == '^');
        if (anchor)
        {
            p++;
            lp--; /* skip anchor character */
        }
        prepstate(&ms, L, s, ls, p, lp);
        do
        {
            const char* res;
            reprepstate(&ms);
            if ((res = match(&ms, s1, p)) != NULL)
            {
                if (find)
                {
                    lua_pushinteger(L, (s1 - s) + 1); /* start */
                    lua_pushinteger(L, res - s);      /* end */
                    return push_captures(&ms, NULL, 0) + 2;
                }
                else
                    return push_captures(&ms, s1, res);
            }
        } while (s1++ < ms.src_end && !anchor);
    }
    lua_pushnil(L); /* not found */
    return 1;
}

static int str_find(lua_State* L) { return str_find_aux(L, 1); }

static int str_match(lua_State* L) { return str_find_aux(L, 0); }

/* state for 'gmatch' */
typedef struct GMatchState
{
    const char* src;       /* current position */
    const char* p;         /* pattern */
    const char* lastmatch; /* end of last match */
    MatchState ms;         /* match state */
} GMatchState;

static int gmatch_aux(lua_State* L)
{
    GMatchState* gm = (GMatchState*)lua_touserdata(L, lua_upvalueindex(3));
    const char* src;
    gm->ms.L = L;
    for (src = gm->src; src <= gm->ms.src_end; src++)
    {
        const char* e;
        reprepstate(&gm->ms);
        if ((e = match(&gm->ms, src, gm->p)) != NULL && e != gm->lastmatch)
        {
            gm->src = gm->lastmatch = e;
            return push_captures(&gm->ms, src, e);
        }
    }
    return 0; /* not found */
}

static int gmatch(lua_State* L)
{
    size_t ls, lp;
    const char* s = luaL_checklstring(L, 1, &ls);
    const char* p = luaL_checklstring(L, 2, &lp);
    GMatchState* gm;
    lua_settop(L, 2); /* keep them on closure to avoid being collected */
    gm = (GMatchState*)lua_newuserdata(L, sizeof(GMatchState));
    prepstate(&gm->ms, L, s, ls, p, lp);
    gm->src = s;
    gm->p = p;
    gm->lastmatch = NULL;
    lua_pushcclosure(L, gmatch_aux, 3);
    return 1;
}

static void add_s(MatchState* ms, luaL_Buffer* b, const char* s, const char* e)
{
    size_t l, i;
    lua_State* L = ms->L;
    const char* news = lua_tolstring(L, 3, &l);
    for (i = 0; i < l; i++)
    {
        if (news[i] != L_ESC)
            luaL_addchar(b, news[i]);
        else
        {
            i++; /* skip ESC */
            if (!isdigit(uchar(news[i])))
            {
                if (news[i] != L_ESC)
                    luaL_error(L, "invalid use of '%c' in replacement string", L_ESC);
                luaL_addchar(b, news[i]);
            }
            else if (news[i] == '0')
                luaL_addlstring(b, s, e - s);
            else
            {
                push_onecapture(ms, news[i] - '1', s, e);
                luaL_tolstring(L, -1, NULL); /* if number, convert it to string */
                lua_remove(L, -2);           /* remove original value */
                luaL_addvalue(b);            /* add capture to accumulated result */
            }
        }
    }
}

static void add_value(MatchState* ms, luaL_Buffer* b, const char* s, const char* e, int tr)
{
    lua_State* L = ms->L;
    switch (tr)
    {
    case LUA_TFUNCTION:
    {
        int n;
        lua_pushvalue(L, 3);
        n = push_captures(ms, s, e);
        lua_call(L, n, 1);
        break;
    }
    case LUA_TTABLE:
    {
        push_onecapture(ms, 0, s, e);
        lua_gettable(L, 3);
        break;
    }
    default:
    { /* LUA_TNUMBER or LUA_TSTRING */
        add_s(ms, b, s, e);
        return;
    }
    }
    if (!lua_toboolean(L, -1))
    { /* nil or false? */
        lua_pop(L, 1);
        lua_pushlstring(L, s, e - s); /* keep original text */
    }
    else if (!lua_isstring(L, -1))
        luaL_error(L, "invalid replacement value (a %s)", luaL_typename(L, -1));
    luaL_addvalue(b); /* add result to accumulator */
}

static int str_gsub(lua_State* L)
{
    size_t srcl, lp;
    const char* src = luaL_checklstring(L, 1, &srcl);    /* subject */
    const char* p = luaL_checklstring(L, 2, &lp);        /* pattern */
    const char* lastmatch = NULL;                        /* end of last match */
    int tr = lua_type(L, 3);                             /* replacement type */
    lua_Integer max_s = luaL_optinteger(L, 4, srcl + 1); /* max replacements */
    int anchor = (*p == '^');
    lua_Integer n = 0; /* replacement count */
    MatchState ms;
    luaL_Buffer b;
    luaL_argcheck(L, tr == LUA_TNUMBER || tr == LUA_TSTRING || tr == LUA_TFUNCTION || tr == LUA_TTABLE, 3, "string/function/table expected");
    luaL_buffinit(L, &b);
    if (anchor)
    {
        p++;
        lp--; /* skip anchor character */
    }
    prepstate(&ms, L, src, srcl, p, lp);
    while (n < max_s)
    {
        const char* e;
        reprepstate(&ms); /* (re)prepare state for new match */
        if ((e = match(&ms, src, p)) != NULL && e != lastmatch)
        { /* match? */
            n++;
            add_value(&ms, &b, src, e, tr); /* add replacement to buffer */
            src = lastmatch = e;
        }
        else if (src < ms.src_end) /* otherwise, skip one character */
            luaL_addchar(&b, *src++);
        else
            break; /* end of subject */
        if (anchor)
            break;
    }
    luaL_addlstring(&b, src, ms.src_end - src);
    luaL_pushresult(&b);
    lua_pushinteger(L, n); /* number of substitutions */
    return 2;
}

/* }====================================================== */

/*
** {======================================================
** STRING FORMAT
** =======================================================
*/

#if !defined(lua_number2strx) /* { */

/*
** Hexadecimal floating-point formatter
*/

#include <math.h>

#define SIZELENMOD (sizeof(LUA_NUMBER_FRMLEN) / sizeof(char))

/*
** Number of bits that goes into the first digit. It can be any value
** between 1 and 4; the following definition tries to align the number
** to nibble boundaries by making what is left after that first digit a
** multiple of 4.
*/
#define L_NBFD ((l_mathlim(MANT_DIG) - 1) % 4 + 1)

/*
** Add integer part of 'x' to buffer and return new 'x'
*/
static lua_Number adddigit(char* buff, int n, lua_Number x)
{
    lua_Number dd = l_mathop(floor)(x); /* get integer part from 'x' */
    int d = (int)dd;
    buff[n] = (d < 10 ? d + '0' : d - 10 + 'a'); /* add to buffer */
    return x - dd;                               /* return what is left */
}

static int num2straux(char* buff, int sz, lua_Number x)
{
    /* if 'inf' or 'NaN', format it like '%g' */
    if (x != x || x == (lua_Number)HUGE_VAL || x == -(lua_Number)HUGE_VAL)
        return l_sprintf(buff, sz, LUA_NUMBER_FMT, (LUAI_UACNUMBER)x);
    else if (x == 0)
    { /* can be -0... */
        /* create "0" or "-0" followed by exponent */
        return l_sprintf(buff, sz, LUA_NUMBER_FMT "x0p+0", (LUAI_UACNUMBER)x);
    }
    else
    {
        int e;
        lua_Number m = l_mathop(frexp)(x, &e); /* 'x' fraction and exponent */
        int n = 0;                             /* character count */
        if (m < 0)
        {                    /* is number negative? */
            buff[n++] = '-'; /* add signal */
            m = -m;          /* make it positive */
        }
        buff[n++] = '0';
        buff[n++] = 'x';                            /* add "0x" */
        m = adddigit(buff, n++, m * (1 << L_NBFD)); /* add first digit */
        e -= L_NBFD;                                /* this digit goes before the radix point */
        if (m > 0)
        {                                        /* more digits? */
            buff[n++] = lua_getlocaledecpoint(); /* add radix point */
            do
            { /* add as many digits as needed */
                m = adddigit(buff, n++, m * 16);
            } while (m > 0);
        }
        n += l_sprintf(buff + n, sz - n, "p%+d", e); /* add exponent */
        lua_assert(n < sz);
        return n;
    }
}

static int lua_number2strx(lua_State* L, char* buff, int sz, const char* fmt, lua_Number x)
{
    int n = num2straux(buff, sz, x);
    if (fmt[SIZELENMOD] == 'A')
    {
        int i;
        for (i = 0; i < n; i++) buff[i] = toupper(uchar(buff[i]));
    }
    else if (fmt[SIZELENMOD] != 'a')
        return luaL_error(L, "modifiers for format '%%a'/'%%A' not implemented");
    return n;
}

#endif /* } */

/*
** Maximum size of each formatted item. This maximum size is produced
** by format('%.99f', -maxfloat), and is equal to 99 + 3 ('-', '.',
** and '\0') + number of decimal digits to represent maxfloat (which
** is maximum exponent + 1). (99+3+1 then rounded to 120 for "extra
** expenses", such as locale-dependent stuff)
*/
#define MAX_ITEM (120 + l_mathlim(MAX_10_EXP))

/* valid flags in a format specification */
#define FLAGS "-+ #0"

/*
** maximum size of each format specification (such as "%-099.99d")
*/
#define MAX_FORMAT 32

static void addquoted(luaL_Buffer* b, const char* s, size_t len)
{
    luaL_addchar(b, '"');
    while (len--)
    {
        if (*s == '"' || *s == '\\' || *s == '\n')
        {
            luaL_addchar(b, '\\');
            luaL_addchar(b, *s);
        }
        else if (iscntrl(uchar(*s)))
        {
            char buff[10];
            if (!isdigit(uchar(*(s + 1))))
                l_sprintf(buff, sizeof(buff), "\\%d", (int)uchar(*s));
            else
                l_sprintf(buff, sizeof(buff), "\\%03d", (int)uchar(*s));
            luaL_addstring(b, buff);
        }
        else
            luaL_addchar(b, *s);
        s++;
    }
    luaL_addchar(b, '"');
}

/*
** Ensures the 'buff' string uses a dot as the radix character.
*/
static void checkdp(char* buff, int nb)
{
    if (memchr(buff, '.', nb) == NULL)
    {                                         /* no dot? */
        char point = lua_getlocaledecpoint(); /* try locale point */
        char* ppoint = (char*)memchr(buff, point, nb);
        if (ppoint)
            *ppoint = '.'; /* change it to a dot */
    }
}

static void addliteral(lua_State* L, luaL_Buffer* b, int arg)
{
    switch (lua_type(L, arg))
    {
    case LUA_TSTRING:
    {
        size_t len;
        const char* s = lua_tolstring(L, arg, &len);
        addquoted(b, s, len);
        break;
    }
    case LUA_TNUMBER:
    {
        char* buff = luaL_prepbuffsize(b, MAX_ITEM);
        int nb;
        if (!lua_isinteger(L, arg))
        {                                        /* float? */
            lua_Number n = lua_tonumber(L, arg); /* write as hexa ('%a') */
            nb = lua_number2strx(L, buff, MAX_ITEM, "%" LUA_NUMBER_FRMLEN "a", n);
            checkdp(buff, nb); /* ensure it uses a dot */
        }
        else
        { /* integers */
            lua_Integer n = lua_tointeger(L, arg);
            const char* format = (n == LUA_MININTEGER) /* corner case? */
                                     ?
                                     "0x%" LUA_INTEGER_FRMLEN "x" /* use hexa */
                                     :
                                     LUA_INTEGER_FMT; /* else use default format */
            nb = l_sprintf(buff, MAX_ITEM, format, (LUAI_UACINT)n);
        }
        luaL_addsize(b, nb);
        break;
    }
    case LUA_TNIL:
    case LUA_TBOOLEAN:
    {
        luaL_tolstring(L, arg, NULL);
        luaL_addvalue(b);
        break;
    }
    default:
    {
        luaL_argerror(L, arg, "value has no literal form");
    }
    }
}

static const char* scanformat(lua_State* L, const char* strfrmt, char* form)
{
    const char* p = strfrmt;
    while (*p != '\0' && strchr(FLAGS, *p) != NULL) p++; /* skip flags */
    if ((size_t)(p - strfrmt) >= sizeof(FLAGS) / sizeof(char))
        luaL_error(L, "invalid format (repeated flags)");
    if (isdigit(uchar(*p)))
        p++; /* skip width */
    if (isdigit(uchar(*p)))
        p++; /* (2 digits at most) */
    if (*p == '.')
    {
        p++;
        if (isdigit(uchar(*p)))
            p++; /* skip precision */
        if (isdigit(uchar(*p)))
            p++; /* (2 digits at most) */
    }
    if (isdigit(uchar(*p)))
        luaL_error(L, "invalid format (width or precision too long)");
    *(form++) = '%';
    memcpy(form, strfrmt, ((p - strfrmt) + 1) * sizeof(char));
    form += (p - strfrmt) + 1;
    *form = '\0';
    return p;
}

/*
** add length modifier into formats
*/
static void addlenmod(char* form, const char* lenmod)
{
    size_t l = strlen(form);
    size_t lm = strlen(lenmod);
    char spec = form[l - 1];
    strcpy(form + l - 1, lenmod);
    form[l + lm - 1] = spec;
    form[l + lm] = '\0';
}

static int str_format(lua_State* L)
{
    int top = lua_gettop(L);
    int arg = 1;
    size_t sfl;
    const char* strfrmt = luaL_checklstring(L, arg, &sfl);
    const char* strfrmt_end = strfrmt + sfl;
    luaL_Buffer b;
    luaL_buffinit(L, &b);
    while (strfrmt < strfrmt_end)
    {
        if (*strfrmt != L_ESC)
            luaL_addchar(&b, *strfrmt++);
        else if (*++strfrmt == L_ESC)
            luaL_addchar(&b, *strfrmt++); /* %% */
        else
        {                                                 /* format item */
            char form[MAX_FORMAT];                        /* to store the format ('%...') */
            char* buff = luaL_prepbuffsize(&b, MAX_ITEM); /* to put formatted item */
            int nb = 0;                                   /* number of bytes in added item */
            if (++arg > top)
                luaL_argerror(L, arg, "no value");
            strfrmt = scanformat(L, strfrmt, form);
            switch (*strfrmt++)
            {
            case 'c':
            {
                nb = l_sprintf(buff, MAX_ITEM, form, (int)luaL_checkinteger(L, arg));
                break;
            }
            case 'd':
            case 'i':
            case 'o':
            case 'u':
            case 'x':
            case 'X':
            {
                lua_Integer n = luaL_checkinteger(L, arg);
                addlenmod(form, LUA_INTEGER_FRMLEN);
                nb = l_sprintf(buff, MAX_ITEM, form, (LUAI_UACINT)n);
                break;
            }
            case 'a':
            case 'A':
                addlenmod(form, LUA_NUMBER_FRMLEN);
                nb = lua_number2strx(L, buff, MAX_ITEM, form, luaL_checknumber(L, arg));
                break;
            case 'e':
            case 'E':
            case 'f':
            case 'g':
            case 'G':
            {
                lua_Number n = luaL_checknumber(L, arg);
                addlenmod(form, LUA_NUMBER_FRMLEN);
                nb = l_sprintf(buff, MAX_ITEM, form, (LUAI_UACNUMBER)n);
                break;
            }
            case 'q':
            {
                addliteral(L, &b, arg);
                break;
            }
            case 's':
            {
                size_t l;
                const char* s = luaL_tolstring(L, arg, &l);
                if (form[2] == '\0')   /* no modifiers? */
                    luaL_addvalue(&b); /* keep entire string */
                else
                {
                    luaL_argcheck(L, l == strlen(s), arg, "string contains zeros");
                    if (!strchr(form, '.') && l >= 100)
                    {
                        /* no precision and string is too long to be formatted */
                        luaL_addvalue(&b); /* keep entire string */
                    }
                    else
                    { /* format the string into 'buff' */
                        nb = l_sprintf(buff, MAX_ITEM, form, s);
                        lua_pop(L, 1); /* remove result from 'luaL_tolstring' */
                    }
                }
                break;
            }
            default:
            { /* also treat cases 'pnLlh' */
                return luaL_error(L, "invalid option '%%%c' to 'format'", *(strfrmt - 1));
            }
            }
            lua_assert(nb < MAX_ITEM);
            luaL_addsize(&b, nb);
        }
    }
    luaL_pushresult(&b);
    return 1;
}

/* }====================================================== */

/*
** {======================================================
** PACK/UNPACK
** =======================================================
*/

/* value used for padding */
#if !defined(LUAL_PACKPADBYTE)
#define LUAL_PACKPADBYTE 0x00
#endif

/* maximum size for the binary representation of an integer */
#define MAXINTSIZE 16

/* number of bits in a character */
#define NB CHAR_BIT

/* mask for one character (NB 1's) */
#define MC ((1 << NB) - 1)

/* size of a lua_Integer */
#define SZINT ((int)sizeof(lua_Integer))

/* dummy union to get native endianness */
static const union
{
    int dummy;
    char little; /* true iff machine is little endian */
} nativeendian = {1};

/* dummy structure to get native alignment requirements */
struct cD
{
    char c;
    union
    {
        double d;
        void* p;
        lua_Integer i;
        lua_Number n;
    } u;
};

#define MAXALIGN (offsetof(struct cD, u))

/*
** Union for serializing floats
*/
typedef union Ftypes
{
    float f;
    double d;
    lua_Number n;
    char buff[5 * sizeof(lua_Number)]; /* enough for any float type */
} Ftypes;

/*
** information to pack/unpack stuff
*/
typedef struct Header
{
    lua_State* L;
    int islittle;
    int maxalign;
} Header;

/*
** options for pack/unpack
*/
typedef enum KOption
{
    Kint,       /* signed integers */
    Kuint,      /* unsigned integers */
    Kfloat,     /* floating-point numbers */
    Kchar,      /* fixed-length strings */
    Kstring,    /* strings with prefixed length */
    Kzstr,      /* zero-terminated strings */
    Kpadding,   /* padding */
    Kpaddalign, /* padding for alignment */
    Knop        /* no-op (configuration or spaces) */
} KOption;

/*
** Read an integer numeral from string 'fmt' or return 'df' if
** there is no numeral
*/
static int digit(int c) { return '0' <= c && c <= '9'; }

static int getnum(const char** fmt, int df)
{
    if (!digit(**fmt)) /* no number? */
        return df;     /* return default value */
    else
    {
        int a = 0;
        do
        {
            a = a * 10 + (*((*fmt)++) - '0');
        } while (digit(**fmt) && a <= ((int)MAXSIZE - 9) / 10);
        return a;
    }
}

/*
** Read an integer numeral and raises an error if it is larger
** than the maximum size for integers.
*/
static int getnumlimit(Header* h, const char** fmt, int df)
{
    int sz = getnum(fmt, df);
    if (sz > MAXINTSIZE || sz <= 0)
        return luaL_error(h->L, "integral size (%d) out of limits [1,%d]", sz, MAXINTSIZE);
    return sz;
}

/*
** Initialize Header
*/
static void initheader(lua_State* L, Header* h)
{
    h->L = L;
    h->islittle = nativeendian.little;
    h->maxalign = 1;
}

/*
** Read and classify next option. 'size' is filled with option's size.
*/
static KOption getoption(Header* h, const char** fmt, int* size)
{
    int opt = *((*fmt)++);
    *size = 0; /* default */
    switch (opt)
    {
    case 'b':
        *size = sizeof(char);
        return Kint;
    case 'B':
        *size = sizeof(char);
        return Kuint;
    case 'h':
        *size = sizeof(short);
        return Kint;
    case 'H':
        *size = sizeof(short);
        return Kuint;
    case 'l':
        *size = sizeof(long);
        return Kint;
    case 'L':
        *size = sizeof(long);
        return Kuint;
    case 'j':
        *size = sizeof(lua_Integer);
        return Kint;
    case 'J':
        *size = sizeof(lua_Integer);
        return Kuint;
    case 'T':
        *size = sizeof(size_t);
        return Kuint;
    case 'f':
        *size = sizeof(float);
        return Kfloat;
    case 'd':
        *size = sizeof(double);
        return Kfloat;
    case 'n':
        *size = sizeof(lua_Number);
        return Kfloat;
    case 'i':
        *size = getnumlimit(h, fmt, sizeof(int));
        return Kint;
    case 'I':
        *size = getnumlimit(h, fmt, sizeof(int));
        return Kuint;
    case 's':
        *size = getnumlimit(h, fmt, sizeof(size_t));
        return Kstring;
    case 'c':
        *size = getnum(fmt, -1);
        if (*size == -1)
            luaL_error(h->L, "missing size for format option 'c'");
        return Kchar;
    case 'z':
        return Kzstr;
    case 'x':
        *size = 1;
        return Kpadding;
    case 'X':
        return Kpaddalign;
    case ' ':
        break;
    case '<':
        h->islittle = 1;
        break;
    case '>':
        h->islittle = 0;
        break;
    case '=':
        h->islittle = nativeendian.little;
        break;
    case '!':
        h->maxalign = getnumlimit(h, fmt, MAXALIGN);
        break;
    default:
        luaL_error(h->L, "invalid format option '%c'", opt);
    }
    return Knop;
}

/*
** Read, classify, and fill other details about the next option.
** 'psize' is filled with option's size, 'notoalign' with its
** alignment requirements.
** Local variable 'size' gets the size to be aligned. (Kpadal option
** always gets its full alignment, other options are limited by
** the maximum alignment ('maxalign'). Kchar option needs no alignment
** despite its size.
*/
static KOption getdetails(Header* h, size_t totalsize, const char** fmt, int* psize, int* ntoalign)
{
    KOption opt = getoption(h, fmt, psize);
    int align = *psize; /* usually, alignment follows size */
    if (opt == Kpaddalign)
    { /* 'X' gets alignment from following option */
        if (**fmt == '\0' || getoption(h, fmt, &align) == Kchar || align == 0)
            luaL_argerror(h->L, 1, "invalid next option for option 'X'");
    }
    if (align <= 1 || opt == Kchar) /* need no alignment? */
        *ntoalign = 0;
    else
    {
        if (align > h->maxalign) /* enforce maximum alignment */
            align = h->maxalign;
        if ((align & (align - 1)) != 0) /* is 'align' not a power of 2? */
            luaL_argerror(h->L, 1, "format asks for alignment not power of 2");
        *ntoalign = (align - (int)(totalsize & (align - 1))) & (align - 1);
    }
    return opt;
}

/*
** Pack integer 'n' with 'size' bytes and 'islittle' endianness.
** The final 'if' handles the case when 'size' is larger than
** the size of a Lua integer, correcting the extra sign-extension
** bytes if necessary (by default they would be zeros).
*/
static void packint(luaL_Buffer* b, lua_Unsigned n, int islittle, int size, int neg)
{
    char* buff = luaL_prepbuffsize(b, size);
    int i;
    buff[islittle ? 0 : size - 1] = (char)(n & MC); /* first byte */
    for (i = 1; i < size; i++)
    {
        n >>= NB;
        buff[islittle ? i : size - 1 - i] = (char)(n & MC);
    }
    if (neg && size > SZINT)
    {                                  /* negative number need sign extension? */
        for (i = SZINT; i < size; i++) /* correct extra bytes */
            buff[islittle ? i : size - 1 - i] = (char)MC;
    }
    luaL_addsize(b, size); /* add result to buffer */
}

/*
** Copy 'size' bytes from 'src' to 'dest', correcting endianness if
** given 'islittle' is different from native endianness.
*/
static void copywithendian(volatile char* dest, volatile const char* src, int size, int islittle)
{
    if (islittle == nativeendian.little)
    {
        while (size-- != 0) *(dest++) = *(src++);
    }
    else
    {
        dest += size - 1;
        while (size-- != 0) *(dest--) = *(src++);
    }
}

static int str_pack(lua_State* L)
{
    luaL_Buffer b;
    Header h;
    const char* fmt = luaL_checkstring(L, 1); /* format string */
    int arg = 1;                              /* current argument to pack */
    size_t totalsize = 0;                     /* accumulate total size of result */
    initheader(L, &h);
    lua_pushnil(L); /* mark to separate arguments from string buffer */
    luaL_buffinit(L, &b);
    while (*fmt != '\0')
    {
        int size, ntoalign;
        KOption opt = getdetails(&h, totalsize, &fmt, &size, &ntoalign);
        totalsize += ntoalign + size;
        while (ntoalign-- > 0) luaL_addchar(&b, LUAL_PACKPADBYTE); /* fill alignment */
        arg++;
        switch (opt)
        {
        case Kint:
        { /* signed integers */
            lua_Integer n = luaL_checkinteger(L, arg);
            if (size < SZINT)
            { /* need overflow check? */
                lua_Integer lim = (lua_Integer)1 << ((size * NB) - 1);
                luaL_argcheck(L, -lim <= n && n < lim, arg, "integer overflow");
            }
            packint(&b, (lua_Unsigned)n, h.islittle, size, (n < 0));
            break;
        }
        case Kuint:
        { /* unsigned integers */
            lua_Integer n = luaL_checkinteger(L, arg);
            if (size < SZINT) /* need overflow check? */
                luaL_argcheck(L, (lua_Unsigned)n < ((lua_Unsigned)1 << (size * NB)), arg, "unsigned overflow");
            packint(&b, (lua_Unsigned)n, h.islittle, size, 0);
            break;
        }
        case Kfloat:
        { /* floating-point options */
            volatile Ftypes u;
            char* buff = luaL_prepbuffsize(&b, size);
            lua_Number n = luaL_checknumber(L, arg); /* get argument */
            if (size == sizeof(u.f))
                u.f = (float)n; /* copy it into 'u' */
            else if (size == sizeof(u.d))
                u.d = (double)n;
            else
                u.n = n;
            /* move 'u' to final result, correcting endianness if needed */
            copywithendian(buff, u.buff, size, h.islittle);
            luaL_addsize(&b, size);
            break;
        }
        case Kchar:
        { /* fixed-size string */
            size_t len;
            const char* s = luaL_checklstring(L, arg, &len);
            luaL_argcheck(L, len <= (size_t)size, arg, "string longer than given size");
            luaL_addlstring(&b, s, len); /* add string */
            while (len++ < (size_t)size) /* pad extra space */
                luaL_addchar(&b, LUAL_PACKPADBYTE);
            break;
        }
        case Kstring:
        { /* strings with length count */
            size_t len;
            const char* s = luaL_checklstring(L, arg, &len);
            luaL_argcheck(L, size >= (int)sizeof(size_t) || len < ((size_t)1 << (size * NB)), arg, "string length does not fit in given size");
            packint(&b, (lua_Unsigned)len, h.islittle, size, 0); /* pack length */
            luaL_addlstring(&b, s, len);
            totalsize += len;
            break;
        }
        case Kzstr:
        { /* zero-terminated string */
            size_t len;
            const char* s = luaL_checklstring(L, arg, &len);
            luaL_argcheck(L, strlen(s) == len, arg, "string contains zeros");
            luaL_addlstring(&b, s, len);
            luaL_addchar(&b, '\0'); /* add zero at the end */
            totalsize += len + 1;
            break;
        }
        case Kpadding:
            luaL_addchar(&b, LUAL_PACKPADBYTE); /* FALLTHROUGH */
        case Kpaddalign:
        case Knop:
            arg--; /* undo increment */
            break;
        }
    }
    luaL_pushresult(&b);
    return 1;
}

static int str_packsize(lua_State* L)
{
    Header h;
    const char* fmt = luaL_checkstring(L, 1); /* format string */
    size_t totalsize = 0;                     /* accumulate total size of result */
    initheader(L, &h);
    while (*fmt != '\0')
    {
        int size, ntoalign;
        KOption opt = getdetails(&h, totalsize, &fmt, &size, &ntoalign);
        size += ntoalign; /* total space used by option */
        luaL_argcheck(L, totalsize <= MAXSIZE - size, 1, "format result too large");
        totalsize += size;
        switch (opt)
        {
        case Kstring: /* strings with length count */
        case Kzstr:   /* zero-terminated string */
            luaL_argerror(L, 1, "variable-length format");
            /* call never return, but to avoid warnings: */ /* FALLTHROUGH */
        default:
            break;
        }
    }
    lua_pushinteger(L, (lua_Integer)totalsize);
    return 1;
}

/*
** Unpack an integer with 'size' bytes and 'islittle' endianness.
** If size is smaller than the size of a Lua integer and integer
** is signed, must do sign extension (propagating the sign to the
** higher bits); if size is larger than the size of a Lua integer,
** it must check the unread bytes to see whether they do not cause an
** overflow.
*/
static lua_Integer unpackint(lua_State* L, const char* str, int islittle, int size, int issigned)
{
    lua_Unsigned res = 0;
    int i;
    int limit = (size <= SZINT) ? size : SZINT;
    for (i = limit - 1; i >= 0; i--)
    {
        res <<= NB;
        res |= (lua_Unsigned)(unsigned char)str[islittle ? i : size - 1 - i];
    }
    if (size < SZINT)
    { /* real size smaller than lua_Integer? */
        if (issigned)
        { /* needs sign extension? */
            lua_Unsigned mask = (lua_Unsigned)1 << (size * NB - 1);
            res = ((res ^ mask) - mask); /* do sign extension */
        }
    }
    else if (size > SZINT)
    { /* must check unread bytes */
        int mask = (!issigned || (lua_Integer)res >= 0) ? 0 : MC;
        for (i = limit; i < size; i++)
        {
            if ((unsigned char)str[islittle ? i : size - 1 - i] != mask)
                luaL_error(L, "%d-byte integer does not fit into Lua Integer", size);
        }
    }
    return (lua_Integer)res;
}

static int str_unpack(lua_State* L)
{
    Header h;
    const char* fmt = luaL_checkstring(L, 1);
    size_t ld;
    const char* data = luaL_checklstring(L, 2, &ld);
    size_t pos = (size_t)posrelat(luaL_optinteger(L, 3, 1), ld) - 1;
    int n = 0; /* number of results */
    luaL_argcheck(L, pos <= ld, 3, "initial position out of string");
    initheader(L, &h);
    while (*fmt != '\0')
    {
        int size, ntoalign;
        KOption opt = getdetails(&h, pos, &fmt, &size, &ntoalign);
        if ((size_t)ntoalign + size > ~pos || pos + ntoalign + size > ld)
            luaL_argerror(L, 2, "data string too short");
        pos += ntoalign; /* skip alignment */
        /* stack space for item + next position */
        luaL_checkstack(L, 2, "too many results");
        n++;
        switch (opt)
        {
        case Kint:
        case Kuint:
        {
            lua_Integer res = unpackint(L, data + pos, h.islittle, size, (opt == Kint));
            lua_pushinteger(L, res);
            break;
        }
        case Kfloat:
        {
            volatile Ftypes u;
            lua_Number num;
            copywithendian(u.buff, data + pos, size, h.islittle);
            if (size == sizeof(u.f))
                num = (lua_Number)u.f;
            else if (size == sizeof(u.d))
                num = (lua_Number)u.d;
            else
                num = u.n;
            lua_pushnumber(L, num);
            break;
        }
        case Kchar:
        {
            lua_pushlstring(L, data + pos, size);
            break;
        }
        case Kstring:
        {
            size_t len = (size_t)unpackint(L, data + pos, h.islittle, size, 0);
            luaL_argcheck(L, pos + len + size <= ld, 2, "data string too short");
            lua_pushlstring(L, data + pos + size, len);
            pos += len; /* skip string */
            break;
        }
        case Kzstr:
        {
            size_t len = (int)strlen(data + pos);
            lua_pushlstring(L, data + pos, len);
            pos += len + 1; /* skip string plus final '\0' */
            break;
        }
        case Kpaddalign:
        case Kpadding:
        case Knop:
            n--; /* undo increment */
            break;
        }
        pos += size;
    }
    lua_pushinteger(L, pos + 1); /* next position */
    return n + 1;
}

/* }====================================================== */

static const luaL_Reg strlib[] = {{"byte", str_byte},
                                  {"char", str_char},
                                  {"dump", str_dump},
                                  {"find", str_find},
                                  {"format", str_format},
                                  {"gmatch", gmatch},
                                  {"gsub", str_gsub},
                                  {"len", str_len},
                                  {"lower", str_lower},
                                  {"match", str_match},
                                  {"rep", str_rep},
                                  {"reverse", str_reverse},
                                  {"sub", str_sub},
                                  {"upper", str_upper},
                                  {"pack", str_pack},
                                  {"packsize", str_packsize},
                                  {"unpack", str_unpack},
                                  {NULL, NULL}};

static void createmetatable(lua_State* L)
{
    lua_createtable(L, 0, 1);       /* table to be metatable for strings */
    lua_pushliteral(L, "");         /* dummy string */
    lua_pushvalue(L, -2);           /* copy table */
    lua_setmetatable(L, -2);        /* set table as metatable for strings */
    lua_pop(L, 1);                  /* pop dummy string */
    lua_pushvalue(L, -2);           /* get string library */
    lua_setfield(L, -2, "__index"); /* metatable.__index = string */
    lua_pop(L, 1);                  /* pop metatable */
}

/*
** Open string library
*/
LUAMOD_API int luaopen_string(lua_State* L)
{
    luaL_newlib(L, strlib);
    createmetatable(L);
    return 1;
}
